Cam Balance Mechanism Systems and Methods

ABSTRACT

Embodiments include a balance mechanism having a first cam and a second cam configured to convert a variable force exerted by the energy storage member into a substantially constant force applied to a mounting portion. The balance mechanism may be useful for balancing forces such that a user can set the height of an electronic display and/or other equipment attached to the balance mechanism at a number of heights within the range of travel allowed by the mechanism. Lift mechanisms, display positioning apparatuses, and height adjustable desks incorporating a multi-cam balance mechanism are also provided. A method of positioning a display is also provided.

CROSS-REFERENCES

This application claims the benefit of U.S. Provisional Application No.61/369,430, filed Jul. 30, 2010, and U.S. Provisional Application No.61/369,392, filed Jul. 30, 2010, the content each of which is herebyincorporated by reference in its entirety.

FIELD

Embodiments of the invention generally relate to an apparatus forbalancing a load.

BACKGROUND

Load balancing mechanisms are often incorporated in devices that provideadjustable positioning of one or more types of equipment. Suchmechanisms can be useful for adjusting forces within a positioningdevice that would otherwise vary depending upon, for example, theparticular load or the particular position of the load within a range ofmovement provided by the positioning device. Some articulatedpositioning devices include load balancing mechanisms particularly inorder to assist an operator with manual positioning of different typesof equipment.

One example of a positioning device that may incorporate a loadbalancing mechanism is a device for positioning an electronic display(e.g., monitor, television, etc.) and/or a computer. Many jobs involveworking with personal computers and/or display monitors. In such jobs,the personal computers and/or display monitors may be used by multipleoperators at different times during a day. In some settings, onecomputer and/or monitor may be used by multiple people of differentsizes and having different preferences in a single day. Given thedifferences in people's size and differences in their preferences, amonitor or display adjusted at one setting for one individual may beinappropriate for another individual. For instance, a child would havedifferent physical space needs than an adult using the same computer andmonitor. Further, a single user may wish to periodically adjust theposition of a display and/or other equipment in order to performoperations in various postures.

For equipment requiring frequent manual adjustment, lift assistance hasbeen provided using gas springs, extension springs, and other types ofenergy providing devices. However, gas springs are costly and wear outover time. In addition, gas springs usually require a significant amountof space, for instance arm length, which can be at a premium in certainapplications. In addition, some types of wire springs provide liftassistance that varies depending upon the extent of the springcompression or extension, which can provide uneven assistance throughthe range of movement and make some movements more difficult for manualoperators.

As adjustable height mechanisms for displays have become more widespreadand users have experienced their advantages, users are more frequentlyadjusting the height of their monitors and other equipment. Further,such adjustments are now more frequently desired over a wide range oftravel. Moreover, as equipment grows in size and weight, ease ofadjustability is an important consideration. While current loadbalancing mechanisms can address some of these issues, there is acontinuing desire to increase weight capacity and/or reduce the size ofpositioning devices in order to accommodate bigger equipment. Inaddition, there is a desire for load balancing mechanisms andpositioning devices which are compact, less costly to manufacture andmaintain, have increased reliability, allow easy adjustability, arescalable to many different sized monitors, are adaptable to provide along range of travel, and/or are adaptable to provide constant supportforce as the equipment is being positioned.

SUMMARY

Embodiments of the invention balancing a load, and more particularlyrelate to balancing forces from a source of variable forces in order toprovide substantially constant forces. According to one aspect of theinvention, a lift mechanism is provided that includes a base, a supportcolumn coupled to the base, a mounting portion movably coupled to thesupport column, an energy storage member coupled to the support column,and a balance mechanism coupled between the energy storage member andthe mounting portion. The balance mechanism includes a first cam, asecond cam rotationally coupled to the first cam, and a wheelrotationally coupled to the first cam and the second cam, wherein thefirst cam and the second cam are configured to convert a variable forceexerted by the energy storage member into a substantially constant forceapplied to the mounting portion.

According to another aspect of the invention, a display positioningapparatus comprising is providing. The display positioning apparatusincludes a base, a support column coupled to the base, a mountingportion movably coupled to the support column, the mounting portioncomprising a display mount for attaching an electronic display, anenergy storage member coupled to the support column, and a balancemechanism coupled between the energy storage member and the mountingportion. The balance mechanism includes a first cam, a second camrotationally coupled to the first cam, and a wheel rotationally coupledto the first cam and the second cam, wherein the first cam, the secondcam and the wheel are coaxially mounted to the base and the first camand the second cam are configured to convert a variable force exerted bythe energy storage member into a substantially constant force applied tothe mounting portion.

Another aspect of the invention provides a height adjustable desk. Thedesk includes a base, a work surface, and at least one lift mechanismcoupled between the base and the work surface. The at least one liftmechanism includes a support column coupled to the base, a mountingportion movably coupled to the support column and fixedly coupled to thework surface, an energy storage member coupled to the support column,and a balance mechanism coupled between the energy storage member andthe mounting portion. The balance mechanism includes a first cam, asecond cam rotationally coupled to the first cam, and a wheelrotationally coupled to the first cam and the second cam, wherein thefirst cam and the second cam are configured to convert a variable forceexerted by the energy storage member into a substantially constant forceapplied to the mounting portion.

Another aspect of the invention provides a method of positioning adisplay. The method includes lifting a display within a vertical rangeof travel, assisting the lifting of the display with a variable forceexerted by an energy storage member, and converting the variable forceexerted by the energy storage member into a substantially constant forceapplied to the display with a balance mechanism. The balance mechanismincludes a first cam, a second cam rotationally coupled to the firstcam, and a wheel rotationally coupled to the first cam and the secondcam, wherein the first cam and the second cam are configured to convertthe variable force exerted by the energy storage member into asubstantially constant force applied to the display.

These and various other features and advantages will be apparent from areading of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of particular embodiments of thepresent invention and therefore do not limit the scope of the invention.The drawings are not to scale (unless so stated) and are intended foruse in conjunction with the explanations in the following detaileddescription. Embodiments of the present invention will hereinafter bedescribed in conjunction with the appended drawings, wherein likenumerals denote like elements.

FIG. 1 is a perspective view of a lift mechanism in accordance with anembodiment of the invention.

FIG. 2 is a partially exploded view of the lift mechanism of FIG. 1.

FIGS. 3A and 3B are partial, exploded views of a bottom portion of thelift mechanism of FIG. 1 in accordance with an embodiment of theinvention.

FIG. 4 is a partial elevation view of a top portion of the liftmechanism of FIG. 1 in accordance with an embodiment of the invention.

FIG. 5 is a perspective view of a bottom portion of the lift mechanismof FIG. 1 in accordance with an embodiment of the invention.

FIGS. 6A and 6B are perspective views of a cam member including a firstcam and a second cam in accordance with an embodiment of the invention.

FIG. 7 is a side plan view of the cam member of FIG. 6A.

FIG. 8 is a perspective view of a wheel in accordance with an embodimentof the invention.

FIG. 9 is a side plan view of the wheel of FIG. 8.

FIG. 10 is a perspective view of a pulley system in accordance with anembodiment of the invention.

FIG. 11 is a side plan view of the pulley system of FIG. 10.

FIGS. 12A and 12B are front perspective views of a positioning apparatusin a lowered position and a raised position, respectively, in accordancewith an embodiment of the invention.

FIGS. 13A and 13B are rear perspective views of a positioning apparatusin a lowered position and a raised position, respectively, in accordancewith an embodiment of the invention.

FIG. 14 is a perspective view of a portion of a balance mechanism in astate corresponding to a first position of a mounting portion.

FIG. 15 is a perspective view of a portion of a balance mechanism in astate corresponding to a second position of a mounting portion.

FIGS. 16A and 160B are front perspective views of a positioningapparatus in a raised position and a lowered position, respectively, inaccordance with an embodiment of the invention.

FIG. 17 is a perspective view of a positioning apparatus including akeyboard work surface in accordance with an embodiment of the invention.

FIG. 18A is a perspective view of a lift mechanism in accordance with anembodiment of the invention.

FIGS. 18B and 18C are cross-sectional views of a bottom portion and atop portion, respectively, of the lift mechanism of FIG. 18A.

FIGS. 19A-19D are perspective views of a height adjustable desk inaccordance with an embodiment of the invention.

FIG. 20A is a perspective view of a lift mechanism in accordance with anembodiment of the invention.

FIG. 20B is a partial sectional view of the lift mechanism of FIG. 20A.

FIGS. 20C-20D are partial perspective views of a top portion of the liftmechanism of FIG. 20A.

FIG. 20E is a cross sectional view of a lift mechanism in accordancewith an embodiment of the invention.

FIG. 20F is partial perspective view of a top portion of the liftmechanism of FIG. 20E.

FIGS. 21A-21B are side elevation views of a height adjustable desk inaccordance with an embodiment of the invention.

FIGS. 21C-21D are perspective views of a height adjustable desk inaccordance with an embodiment of the invention.

FIG. 22A is a cross-sectional view of a lift mechanism in accordancewith an embodiment of the invention.

FIG. 22B is a cross-sectional view of a bottom portion of the liftmechanism of FIG. 22A in accordance with an embodiment of the invention.

FIG. 22C is a partial top view of the lift mechanism of FIG. 22A inaccordance with an embodiment of the invention.

FIG. 23A is a side elevation view of a height adjustable desk inaccordance with an embodiment of the invention.

FIG. 23B is a perspective view of the height adjustable desk of FIG.23A.

FIG. 24A is a perspective view of a height adjustable desk in accordancewith an embodiment of the invention.

FIG. 24B is another perspective view of the height adjustable desk ofFIG. 24A in accordance with an embodiment of the invention.

FIG. 24C is a partial perspective view of a brake mechanism of theheight adjustable desk of FIG. 24A in accordance with an embodiment ofthe invention.

FIG. 24D is a partial top view of the height adjustable desk of FIG. 24Ain accordance with an embodiment of the invention.

FIG. 24E is a partial top view of a lift mechanism of the heightadjustable desk of FIG. 24A in accordance with an embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following detailed description is exemplary in nature and is notintended to limit the scope, applicability, or configuration of theinvention in any way. Rather, the following description provides somepractical illustrations for implementing exemplary embodiments of thepresent invention. Examples of constructions, materials, dimensions, andmanufacturing processes are provided for selected elements, and allother elements employ that which is known to those of ordinary skill inthe field of the invention. Those skilled in the art will recognize thatmany of the noted examples have a variety of suitable alternatives.

Some embodiments of the invention generally provide a load balancingmechanism that can be used to balance a wide variety of loads. As justone example, some embodiments include a lift mechanism that incorporatesa load balancing mechanism. Additional embodiments provide a loadbalancing mechanism within other types of positioning device providingmovement through one or more variously oriented ranges of travel. Someembodiments of the invention generally provide apparatuses capable ofpositioning various equipment relative to a human operator. For example,in some cases a positioning apparatus including a load balance mechanismcan support items such as electronic displays, a laptop computer (i.e.,notebook), a keyboard, and/or other computing equipment, such as amouse. As used herein, the term electronic display is used to refer totelevisions, computer monitors, tablet computers, and other types ofdisplays capable of displaying images from electronic signals. Theembodiments discussed herein provide several examples of lift mechanismsand positioning apparatuses incorporating load balance mechanisms thatare capable of positioning such types of computing equipment. However,it is contemplated that embodiments of the invention can be used forpositioning a wide variety of items and the scope of the invention isnot limited in this regard.

FIG. 1 is a perspective view of a lift mechanism 100 incorporating aload balance mechanism 116 in accordance with an exemplary embodiment ofthe invention. The lift mechanism 100 can be useful for lifting avariety of loads, including electronic displays and/or computer-relatedequipment as will be discussed further herein. The lift mechanism 100 ofFIG. 1 comprises a base 102 and a generally vertical support column 106(sometimes referred to as a “riser”) connected to the base 102. The basemay include any structure for supporting the lift mechanism. In someembodiments, the base may include a relatively flat horizontal surfaceuseful for placement on a horizontal work surface. In other embodiments,the base 102 includes a clamp to clamp the lift mechanism to ahorizontal surface or a wall bracket to attach the lift mechanism 100 toa vertical wall. Portions of the balance mechanism 116 can also be seenin FIG. 1. As will be described in more detail herein, the portions ofthe balance mechanism shown in FIG. 1 include a wheel 120, a first cam124, a second cam 126, and a pulley system 130.

The support column 106 can be connected to the base by any suitablemethod. In some embodiments, the support column 106 is pivotablyconnected to the base such that the support column can pivot withrespect to the base 102. In the embodiment shown in FIG. 1, the supportcolumn 106 is connected to the base 102 at an angle. The angle is usefulfor positioning the center of gravity of the monitor or other equipmentcarried by the support at a desired position with respect to the base toenhance stability. The support column 106 can be connected to the base102 at any desired angle, including 90 degrees, less than 90 degrees, ormore than 90 degrees. As shown in FIGS. 12A and 12B, the angle issomewhat more than 90 degrees.

FIG. 2 is a partially exploded view of FIG. 1. In FIG. 2, it can be seenthat the generally vertical support column 106 includes a first portion136 and a second portion 140. As shown in FIG. 4, once fully assembled,a mounting portion 150 (e.g., sometimes referred to herein as a “truck”)is coupled to the second portion 140. The mounting portion 150 and thesecond portion 140 are disposed in sliding engagement with one anothersuch that the mounting portion can translate with respect to the secondportion 140. For example, in some embodiments the second portion 140includes a guide system, such as one or more rails 141 and the mountingportion 150 includes wheels or sliders that roll or slide along therails. In general, the first portion 136 and second portion 140 areconnected to base 102, and the mounting portion 150 can be connected tovarious types of equipment (e.g., one or more monitors and/or othercomputing equipment) that translate along with the mounting portion 150with respect to the first and the second portions 136, 140. As shown inFIG. 2, an energy storage member 144 is coupled to the second portion140. In this example the energy storage member 144 includes an extensionspring, though it may optionally include any device useful for storingpotential energy, including other types of springs (e.g., an extensionspring, compression spring, torsion spring, etc.). In some embodimentsthe energy storage member 144 can be optionally adjustable via an energystorage member adjustment mechanism 146. In this example the adjustmentmechanism 146 includes a threaded bolt with a bracket that changes theeffective at-rest length of the energy storage member when actuated.

Returning to FIG. 1, the lift mechanism 100 provides a generallyvertical range of travel 190 through which the mounting portion 150 (notshown in FIG. 1) can move. In some embodiments, the vertical range oftravel 190 extends between a sitting height and a standing height, thusallowing an operator to use the lift mechanism 100 from both a sittingposition and a standing position. For example, in certain embodimentsthe range of travel 190 is at least about 14 inches. In some embodimentsthe range of travel 190 is between about 14 inches and about 24 inches.The lift mechanism 100 in the positioning apparatus may also providemultiple positions at intermediate heights between the lowest andhighest extents of the range of travel 190, thus accommodating otherworking positions and/or operators of different heights. In some cases adiscrete number of intermediate positions are provided. In some casesthe lift mechanism 100 provides an infinite number of intermediatepositions within the vertical range of travel 190.

The balance mechanism 116 provides a balancing force between the firstand second portions of the generally vertical support column 106 and themounting portion 150, such that an operator can position equipmentattached to the mounting portion at any desired height along the rangeof travel having only to overcome the friction of the system. Further,because of the balancing force provided by the balance mechanism, themounting portion will hold its set position without the user having toengage any locks.

In the embodiment of FIGS. 1 and 2, the wheel 120 is coupled to thefirst cam 124 and the second cam 126. The wheel 120 is rotationallyfixed with respect to the cams such that the first and the second cams124, 126 rotate along with rotation of the wheel. As shown, the firstcam 124 and the second cam 126 can be provided as a single integral cammember. In addition, the wheel and cam member may be provided asdifferent pieces connected directly together through axle 121. In otherembodiments, they may be integrally formed and/or separated by adistance when installed. FIGS. 6A, 6B, and 7 provide perspective andside elevation views of a cam member including both the first and thesecond cams 124, 126 in accordance with an embodiment of the invention.FIGS. 8 and 9 provide perspective and side elevation views of the wheel120 in accordance with an embodiment of the invention.

FIGS. 3A and 3B provide additional perspective views of the balancemechanism 116, illustrating an arrangement of the wheel 120, the firstand the second cams 124, 126, a pulley system 130, and the energystorage member 144 in accordance with an embodiment of the invention.Although not shown, in some embodiments of the invention the first andthe second cams 124, 126 are directly coupled to the energy storagemember 144 via one or more flexible elements that are routed aroundpulley system 130. For example, two flexible elements could be attachedto the end of the energy storage member 144, routed around the pulleysystem 130, and then coupled the cams 124, 126. The flexible element canbe a rope or cable and can include any material useful for transmittingforce, such as a tensile polymer.

Referring to FIG. 3B, in some cases first cam 124 and second cam 126 arecoupled indirectly to the energy storage member 144 via the pulleysystem 130. FIGS. 10 and 11 illustrate one embodiment of the pulleysystem 130, which includes first and second cam pulleys 164, 168, and anenergy storage member pulley 160 coupled between the cam pulleys. Asshown, in some embodiments the energy storage member pulley 160 and thecam pulleys 164, 168 are provided in a single piece construction thoughthis is not required.

Referring to FIG. 11, in this embodiment the pulley system 130 includesa through hole 131, through which a single flexible element 132 can bethreaded and then coupled to the cams 124, 126, one at each end. Such anarrangement is illustrated in FIG. 3B. As the cams rotate and pull (orloosen) flexible element 132, the flexible element 132 engages with thecam pulleys, and is unwound from (or wound around, respectively) each ofthe cam pulleys. An independent, separate flexible element 161 iscoupled between the energy storage member 144 and the energy storagemember pulley 160. The energy storage member pulley 160 rotates with thecam pulleys and thus winds and unwinds the flexible element 161 in orderto engage the energy storage member 144.

Although not shown, in some embodiments each of the first and the secondcams 124, 126 are optionally coupled to one of the cam pulleys 164, 168with an independent, separate flexible element, while energy storagemember pulley 160 is coupled to the energy storage member 144 via theseparate flexible element 161.

Continuing with reference to FIG. 3B and 4, the wheel 120 is coupled tothe mounting portion 150 coupled to the support column 106 with anotherflexible element 135. As the wheel 120 rotates with respect to the base102, the mounting portion 150 moves with respect to the support columnand vice versa. As shown in FIGS. 2 and 3B, an additional directionchanging pulley 134 can direct the flexible element 135 between thewheel 120 and the mounting portion 150. Turning to FIG. 4, the directionof the flexible element 135 is again changed by an upper pulley 138 andthe flexible element 135 is coupled to the mounting portion 150 using ahook 139 or another similar device known in the art.

FIG. 5 is a partial perspective view of a bottom portion of the liftmechanism 100 having a slightly different base configuration than thatshown in FIGS. 1-3B. As discussed above, the energy storage memberpulley 160 is coupled to the energy storage member 144 via a separateflexible element 161. In some cases the energy storage member 144includes a hook 162 that allows for easily coupling the flexible element161 to member 144. In this embodiment, the energy storage member 144 ispositioned within the support column 106 such that the hook 162 isgenerally aligned with the outer edge of the pulley system 130, andspecifically with the outer edge of the energy storage member pulley160. In some embodiments the energy storage member 144 and the pulley160 may be positioned such that a longitudinal axis of the energystorage member is generally tangential to the edge of the pulley 160.

As the energy storage member pulley 160 rotates, it winds or unwinds theflexible element 161, allowing the energy storage member 144 to contractor causing the energy storage member to extend. Accordingly, the forceor weight of the mounting portion 150, as well as any equipment coupledthereto, can be offset by the energy storage member 144, through thetransmission and redirection of force through the flexible elements,pulleys, wheel and cams to the energy storage member 144.

FIGS. 6A and 6B provide perspective views, and FIG. 6C is a side view ofa cam member 200 incorporating the first and the second cams 124, 126according to some embodiments. As shown, the first cam 124 and thesecond cam 126 are incorporated into the single integral cam member 200,though this is not a requirement and the invention is not intended to belimited to this example. Some embodiments may have multiple separatecams that rotate together (e.g., rotationally synchronized about anaxle), multiple cams integrated together into a single member, or acombination of both approaches. Returning to FIGS. 6A and 6B, the cams124, 126 each include an attachment post 123, 129 for fixing the ends ofthe flexible element 132 to the cams as shown in FIG. 3B. The cams 124,126 also each include a camming surface 125, 127 upon which each end ofthe flexible element 132 winds. According to some embodiments, the cammember 200 (or alternatively, the cams 124, 126 individually) can beformed from die cast, molded ABS plastic or nylon, or machined aluminum,among other suitable materials.

According to one example, as the energy storage member 144 (in this casean extension spring) contracts, it applies a linear force to theflexible element 161, which then applies a torque through the pulleysystem 130 and flexible element 132 to the cams 124, 126, thus urgingrotation of the cams 124, 126 in a first direction. The torque appliedby the energy storage member also urges rotation of the wheel 120 in thefirst direction since the wheel is rotationally clocked with the cams.As the wheel 120 rotates in the first direction, it winds the flexibleelement 135, thus pulling the mounting portion 150 (FIG. 4) up relativeto the support column 106.

According to some embodiments, the energy storage member 144 does notexert a constant linear force on the flexible element 161. For example,an extension spring will exert a linear force that varies with theamount of extension or contraction of the spring. However, in someembodiments it is desirable to provide a relatively constant liftingforce for the mounting portion 150, as a constant force tends to makeadjustment of the lift mechanism easier and more ergonomically-friendlyfor operators. In some useful embodiments of the invention, the firstand the second cams 124, 126 are cooperatively shaped and positioned tobalance a force exerted on the wheel 120 by the mounting portion 150with forces exerted by the energy storage member 144 on the cams 124,126. For example, the cams may be shaped and positioned so that avarying torque applied to the cams by the flexible element 161 (via thevarying linear force that the energy storage member exerts) is convertedto a substantially constant torque applied to the wheel 120. The wheel120 then relays the constant torque to the flexible element 135,creating a constant linear force for lifting the mounting portion 150relative to the support column 106. The opposite effect takes place asthe mounting portion 150 is lowered, with the balance mechanism 116creating a substantially constant resistance against downward movementof the mounting portion.

In some embodiments, the effective radius of each cam 124, 126 varies asa function of the angular orientation of the wheel 120 in order toconvert the varying torque to a constant torque. For example, theeffective radius of each cam surface 125, 127 may decrease according toa predetermined force profile as each cam surface winds about therotational axis of the cam member 200 between an outside (e.g.,perimeter) of the cam and the axis. In some cases the force profile is afunction of the displacement of the energy storage member 144. Accordingto some embodiments, the two cams 124, 126 are mirror images of eachother, and have the same profile of radius variation as a function ofrotation. For example, the cams 124, 126 may be symmetrically formedabout a plane that is perpendicular to the cam member's axis ofrotation. However, this is just one example and is not required in allembodiments.

In some embodiments the first and the second cams 124, 126 are eachdesigned to distribute approximately half of the lift force from theenergy storage member 144 to the mounting portion 150 and any attachedequipment. Referring to FIG. 3B, the pulley system 130, including theenergy storage member pulley 160 and the two cam pulleys 164, 168,divide the force from the energy storage member 144 approximately inhalf. The cam pulley 164 then transmits about one half of the force tothe second cam 126, and the cam pulley 168 transmits about one half ofthe force to the first cam 124. Although not shown, the same effect canalso be achieved using separate flexible elements rather than the singleflexible element 132, with the separate flexible elements eithercoupling the cams directly to the energy storage member 144, orindirectly through the pulley system 130.

Applicants have found that apportioning the force from the energystorage member 144 between the first cam and the second cam (or anydesired number of cams) appears to decrease stress and fatigue on theflexible element 132, thus increasing the life of the balance mechanism116 and lift mechanism 100 as will be discussed further herein. Reducingthe amount of stress on the flexible element coupled to each cam alsoallows for a smaller radius of the cam, since the stress on the flexibleelement caused by the smaller radius is offset to some degree by thesmaller force on each flexible element from the energy storage member144. In addition, the ability to use a smaller radius for the cams inturn enables use of a smaller wheel 120. For example, in order to reducethe radius of the wheel 120 and still provide the same amount of lineartravel for the mounting portion 150, the wheel 120 will need to rotatethrough more rotations. This will in turn cause more rotations of thecams 124, 126, which requires a smaller final cam radius in order towind the flexible element 132 the same amount. Dividing the force fromthe energy storage member enables this reduction in radius. Accordingly,the size of the housing covering the balance mechanism 116 can be madesmaller due to the smaller size of the wheel 120 and the cam member 200.

Some embodiments of the invention provide various types of balancemechanisms, lift mechanisms and positioning devices in differentcombinations according to embodiments of the invention. An example of apositioning apparatus 300 according to one embodiment of the inventionwill now be described with reference to FIGS. 12A-13B. FIGS. 12A and 12Bshow the positioning apparatus 300 in a lowered position and a raisedposition, respectively, from a front perspective. FIGS. 13A and 13B arerear perspective views of the positioning apparatus 300 in a loweredposition and a raised position, respectively, without the supporteddisplay and notebook. Referring to FIGS. 12A-13B, the positioningapparatus 300 supports an electronic display in the form of a computermonitor 302, in addition to a notebook computer 304 in accordance withan embodiment of the invention. The positioning apparatus 300 includes abase 310 and a generally vertical support column 312 connected to thebase 310. A movable mounting portion 350 is movably coupled to thesupport column 312 and attaches the monitor 302 and notebook 304 to theapparatus. In some cases the mounting portion 350 may also movablycouple a keyboard tray 355 and a mouse tray 357 to the support column312.

Referring to FIGS. 13A and 13B, the apparatus 300 includes a crossbar360 attached to the mounting portion 350 for mounting various equipment.For example, in some cases a monitor mount 362 (e.g., a standard VESAconnector), notebook tray 364, and/or other equipment mounts areattached to the crossbar 360, allowing the mounting portion 350 tosupport and move the monitor, notebook, and/or other equipment. Itshould be appreciated, however, that a wide variety of equipment can bemoved by the mounting portion 350 and that the scope of the invention isnot limited in this manner. For example, the mounting portion 350 may beconfigured to support and move a combination of one or more monitorsand/or notebooks or other equipment. In some embodiments the mountingportion 350 is configured to support and move a combination of monitorsand notebooks (e.g., two monitors and a notebook, three monitors and anotebook). In some embodiments the mounting portion 350 is configured tosupport and move multiple monitors, such as sets of two, three, or fouror more monitors.

As shown in FIGS. 12A, 12B, 13A, and 13B, the positioning apparatus 300can provide a wide range of travel 390 for the attached monitor andnotebook. According to some embodiments, the height of the equipment(and mounting portion 350) can be set to any one of an infinite numberof heights within the range of travel 390. FIGS. 12A and 13A illustratepositioning apparatus 300 in a low position (e.g., for sitting), whileFIGS. 12B and 13B illustrate positioning apparatus 300 in a highposition (e.g., for standing). To provide such adjustability for themonitor 302 and the notebook 304, positioning apparatus 300 in thisembodiment includes the lift mechanism 100 and the balance mechanism 116shown in FIGS. 1-11 and described above. FIGS. 13A and 13B illustratethe lift mechanism and the balance mechanism 116 incorporated intopositioning apparatus 300. The wheel 120, as well as first and secondcams 124, 126, and pulley system 130 (not shown) are positioned withinthe base 310. The energy storage member 144, in this case an extensionspring, is positioned within the support column 312 and coupled betweenthe support column 312 and the remaining portion of the balancemechanism.

According to some embodiments, the mounting portion 350 can itselfprovide some degree of adjustability between attached components. Forexample, as shown in FIGS. 12A, 12B, 13A, and 13B, in some cases asecond lift mechanism is incorporated within or attached to the mountingportion 350. This can advantageously allow, for example, the crossbar360, monitor 302 and the notebook 304 to be height adjusted with respectto the keyboard tray 355 to accommodate different users. The second liftmechanism can be any suitable mechanism known in the art. In someembodiments, the second lift mechanism includes a mechanism such as oneof those taught in presently co-owned US Patent Application PublicationUS 2006/0185563 A1, which application was filed Sep. 28, 2005, theentire contents of which is incorporated by reference herein.

In the embodiment shown in FIGS. 12A and 12B, the support column 312 isconnected to the base 310 at an angle, which is useful for positioningthe center of gravity of the monitor 302 and notebook 304 at a desiredlocation with respect to the base 310 to enhance stability. The supportcolumn 312 can be connected to the base at any desired angle, including90 degrees, less than 90 degrees, or more than 90 degrees. As shown inFIGS. 12A and 12B, the angle is somewhat more than 90 degrees. Accordingto some embodiments, the positioning apparatus 300 is advantageouslyconfigured to be used with an existing horizontal work surface 316, suchas a desk or table. For example, base 310 may include multiplestabilizing legs 370 that hold the apparatus 300 upright on the worksurface 316. In some cases base 310 includes a clamp 314 useful forsecuring positioning apparatus 300 to the horizontal work surface 316.

A positioning apparatus can include a base encompassing any structurethat adequately supports the support column and the mounting portionupon a work surface. With continuing reference to FIGS. 12A-13B,according to some embodiments of the invention, the base 310 includes afirst end and a second end with an elongated section extending betweenthe first and the second ends. According to some embodiments, portionsof the elongated section are formed with a low profile, thus minimizingany obstruction caused by the base and maximizing the range of travel ofthe mounting portion 350. In some cases the elongated section of thebase 310 is generally parallel to the mounting portion 350.

In addition, in some cases the elongated section has a widthapproximately the same as a width of the mounting portion frame directlyabove the base and the support column 312. Such a configuration canadvantageously reduce the footprint of the base 310 upon the worksurface, thus leaving more room for other activities as well as reducingthe visual impact of the positioning apparatus. For example, in someembodiments the widths of the elongated section of the base, the frameof the mounting portion, and the support column 312 are equal to or lessthan about 5 inches. In some cases, the widths of the elongated section,the frame of the mounting portion, and the support column 312 are equalto or less than a width of an electronic display mount (e.g., a VESAmount) attached to the mounting portion.

In some embodiments, the vertical range of travel 390 of the positioningapparatus 300 extends between a sitting height and a standing height,thus allowing an operator to use the apparatus 300 from both a sittingposition and a standing position. For example, in certain embodimentsthe range of travel 390 is at least about 14 inches. In some embodimentsthe range of travel 390 is between about 14 inches and about 24 inches.The lift mechanism 100 in the positioning apparatus may also providemultiple positions at intermediate heights between the lowest andhighest extents of the range of travel 390, thus accommodating otherworking positions and/or operators of different heights. In some cases adiscrete number of intermediate positions are provided. In some casesthe lift mechanism 100 provides an infinite number of intermediatepositions within the vertical range of travel 390.

According to some embodiments of the invention, the positioningapparatus 300 is useful in applications in which a single operator maywish to both sit and stand while using the same monitor and/or notebook.For convenience, the positioning apparatus 300 can be described for suchuses as a “sit-stand” positioning apparatus. Such sit-stand apparatusescan be useful in situations in which operators desire to performoperations in various postures, which may be required or desired to beperformed at the same workstation. For example, one may desire toperform some operations in a seated position and other operations in astanding position. Certain embodiments of the invention provide a uniquesit-stand positioning apparatus that is compatible with an existing,independent work surface (e.g., a desk top, table top, counter top,etc.) to form a sit-stand workstation. The positioning apparatus allowsan operator to use the workstation at multiple heights if desiredwithout the need for separate work surfaces at multiple heights.Accordingly, an operator does not need to move to a differentworkstation, but can adjust the height of the sit-stand workstation andcontinue using the existing workstation at the new height. Sit-standpositioning apparatuses may be subjected to more frequent adjustment(e.g., several times in a work day) than traditional, stationary monitormounts, and embodiments incorporating multiple cam members as discussedabove are thought to increase the cycle life of the apparatus as itencounters increased articulation. Further, some embodiments allow forrelatively large ranges of travel while occupying a smaller footprint ona work surface where space is valuable.

In use, when an operator desires to change the position of a monitor orother device supported by the positioning apparatus 300, the operatorcan apply a force to the monitor and/or notebook. Movement of themonitor causes the mounting portion 350, to which it is attached, toalso move relative to the support column 312 of the apparatus. FIG. 14is a perspective view of a portion of the balance mechanism 116 in astate corresponding to the low position of mounting portion 350, whileFIG. 15 is a perspective view of a portion of balance mechanism 116 in astate corresponding to the high position of mounting portion 350. As isshown, the mounting portion 350 is attached to the wheel 120 viaflexible element 135, so that movement of the monitor/notebook causesthe wheel 120 to turn about its axis. The first and second cams 124,126, which are attached to the wheel 120, also rotate and cause the campulleys 164, 168 and energy storage member pulley 160 to rotate abouttheir respective axes (which in this case are the same axis). Rotationof the energy storage member pulley 160 pulls or loosens flexibleelement 161, causing the energy storage member 144 to expand or allowingthe member to contract in length. Since the shape of the cams 124, 126are designed to accommodate a changing energy storage member force(e.g., based on spring length), the operator only need apply arelatively constant force to overcome friction to move the monitor toany desired position, and the monitor will stay in the desired positionwithout having to lock it into that position.

Balance mechanisms including multiple cams as described above, and liftmechanisms and other types of positioning devices incorporatingcorresponding balance mechanisms, provide for surprising advantages overbalance mechanisms that use a single cam. For example, balancemechanisms using multiple cams are more robust and reliable than singlecam mechanisms. Applicants have surprisingly found that using a dual camas described above can withstand a substantially greater number ofcycles of adjustment compared to analogous single cam balancemechanisms. As just one example, Applicants have surprisingly found thatincreasing the number of cams within the balance mechanism by a factorof N can in some cases increase the load life of the mechanism by morethan a factor of N. In some cases Applicants have found the load life toincrease by a factor of 1.5N. In one case, Applicants surprisingly foundthat utilizing a balance mechanism including a dual cam as describedherein increased the cycle life to 28,000 cycles from a cycle life of10,000 cycles for a single cam mechanism under substantially similarconditions. Such an improved cycle life can increase the usefulness ofpractically any positioning apparatus, and provides an especiallyapplicable and unexpected improvement for positioning apparatuses suchas sit/stand positioning apparatuses that are subjected to a greaternumber of articulations than stands that are not able to accommodate asingle operator in both sitting and standing postures.

Positioning apparatuses employing multiple cams also allow for heavierloads to be translated over a larger distance with a smaller cam housingsize than analogous single cam balance mechanisms. This feature isparticularly useful in positioning apparatuses that are designed to siton top of a horizontal work surface and to accommodate an operator inboth sitting and standing positions as they allow for relatively largeranges of travel while occupying a smaller footprint on a work surfacewhere space is valuable. As one example, a positioning apparatusaccording to one embodiment includes a housing that accommodates a dualcam (e.g., first and second cams in FIGS. 1 and 2) that providescounterbalanced movement for an approximately 90 lbs. load over adistance of about 20 inches. In some cases this housing has anapproximate size of 180 mm×125 mm×95 mm. In contrast, a housing for asingle cam mechanism configured for a substantially similar load anddistance can require a housing that is approximately 228 mm×203 mm×90mm. Accordingly, such embodiments are useful for work surface top standswhere space conservation is important. Of course the housing size may besmaller or larger, depending upon the particular weight and distancerequirements for a particular apparatus. Some embodiments can be scaledto accommodate weights between about 3 lbs. and about 250 lbs. or more,and ranges of travel between about 2-3 inches up to 40 inches or more.

Without being bound by theory, Applicants believe that embodimentsincluding multiple cams (e.g., a dual cam) provide advantages oversingle cam balance mechanisms because dividing the force of the attachedequipment among two or more cams allows for a smaller force, and thusless stress, on each cam and associated flexible element, leading to anincreased useful product life. In addition, each individual cam can bemade smaller due to the smaller amount of load on each cam, while thefull load can be carried by a single flexible element that wraps aroundthe larger diameter of energy storage member pulley.

The following examples are presented to further illustrate embodimentsof the multi-cam member (e.g., dual cam) described herein, and are notintended to limit the scope of the invention.

EXAMPLE 1 Comparable Example of Cycle Failure

Testing was carried out on a number of single cam balance mechanismsusing an air cylinder with a 20″ stroke. The single cam balancemechanisms each included a molded cam and other manufactured componentsincluding an extension spring and rope made according to specificationto balance the desired weight over the desired range. The balancemechanisms were adjusted to a maximum weight to be balanced in order toapply the most stress to the rope. The air cylinder was connected to themoving component of the engine, and was cycled through its travel rangeat a rate of 6 cycles per minute. A targeted cycle life of 10,000 cyclesunder maximum loading was expected. In most cases, failure of the ropeoccurred at slightly more than 10,000 cycles but less than 12,500cycles.

EXAMPLE 2 Cycle Failure of an Exemplary Dual Cam

Testing was carried out on a dual cam balance mechanism. Test set up,loading, cycle rate, rope material, weight range, and travel range wereall identical to those in the testing of single cam mechanisms describedin Example 1. Design differences included differences in cam design,spring design, and rope routing to accommodate the dual cam design. Inat least one test of this configuration, the mechanism exceeded 28,000cycles.

Turning to FIGS. 16A and 16B, another example of a positioning apparatus400 according to some embodiments will be described. FIGS. 16A and 16Bare schematic representations of front perspective views of apositioning apparatus 400 in a raised position and a lowered position,respectively, in accordance with an embodiment of the invention. Theapparatus includes a base 402, which in this case is attached to a worksurface 404 at a front end of the base. Although not shown, a supportcolumn 406 is movably coupled to a mounting portion with a liftmechanism and a balance mechanism (located in a housing 420 attached tothe base 402), such as one of those described herein. The mountingportion (not shown) supports a display 408 attached to a display mount.The mounting portion also includes a keyboard arm 410 and a coupledkeyboard tray 412. The mounting portion (again, not separately shown) isconfigured so that as the mounting portion moves up and down relative tothe support column 406, the keyboard tray 412 and display 408 move upand down through a generally vertical range of travel 414. As shown inFIGS. 16A and 16B, the vertical range of travel of the keyboard tray 412is entirely above the work surface 404 in this embodiment. The apparatus400 thus provides a multi-position workstation that allows the keyboardtray 412 and the display 408 to be moved between two or more positions(e.g., heights) above the work surface 404. In some embodiments thepositioning apparatus 400 also includes an attachment mechanism (e.g., aclamp) for removably or fixedly attaching the apparatus to the existingwork surface 404. The attachment mechanism can provide an added amountof stability versus simply resting upon the work surface 404. However,an attachment mechanism is not required and in some cases thepositioning apparatus may simply sit on the work surface 404.

FIG. 17 is a perspective, schematic illustration of another positioningapparatus 450 including a keyboard work surface 462 in accordance withan embodiment of the invention. The positioning apparatus 450 includes abase 452 attached to the work surface 454 at a front end of the base.Although not shown, a support column 456 is movably coupled to amounting portion with a lift mechanism and a balance mechanism (locatedin a housing 458 attached to the base 452), such as one of thosedescribed herein. The mounting portion (not shown separately) alsosupports a display 460 attached to a display mount. The mounting portionalso includes a movable work surface 462. The work surface 462 functionsas a keyboard tray, but also provides a work area that can be useful to,e.g., read or mark up paper documents, support various items, etc. Insome embodiments the positioning apparatus 450 also includes anattachment mechanism (e.g., either removably with a clamp, or fixedlywith an adhesive or other fastener) for removably or fixedly attachingthe apparatus to the existing work surface 454. The attachment mechanismcan provide an added amount of stability versus simply resting upon thework surface 454. However, an attachment mechanism is not required andin some cases the positioning apparatus may simply sit on the worksurface 454.

Turning to FIGS. 18A-18C, another example of a lift mechanism 500 isillustrated according to an embodiment of the invention. FIG. 18A is aperspective view of the lift mechanism 500, and FIGS. 18B and 18C arecross-sectional views of a bottom portion and a top portion,respectively, of the lift mechanism 500. The lift mechanism 500 includesa base 502 connected to a support column 504 (sometimes referred to as a“riser”). A mounting portion 506 is movably coupled to the supportcolumn 504 and configured to move up and down the support column 504through a generally vertical range of travel 508. An energy storagemember 544 is coupled to the mounting portion 506 for providing liftassistance. The lift mechanism includes an upper spring guide andattachment member 546 that attaches the energy storage member to thesupport column. The member 546 also guides adjustment of the tension ofthe energy storage member through an optional adjustment screw 547. Alower spring guide 548 is provided at the opposite end of the storagemember to guide movement of the energy storage member as it extends andcontracts. The lift mechanism 500 also includes a balance mechanismcoupled between the mounting portion 506 and the energy storage member544 for balancing forces between the energy storage member 544 and themounting portion 506.

In this example, the lift mechanism 500 includes a balance mechanism 516substantially similar to the balance mechanism 116 described above withrespect to FIGS. 1-9. Turning to FIG. 18B, the balance mechanism 516includes a wheel 520 that is rotationally coupled to a cam member 550that includes two separate cams. A pulley system 530 includes dual campulleys that are coupled to the cams via flexible elements (not shown)and an energy storage member pulley coupled to the energy storage member544 via another flexible element (not shown). As with the example inFIGS. 1-9, two direction-changing pulleys including a lower pulley 534and an upper pulley 538 (see FIG. 18C) route another flexible element(not shown) between the mounting portion 506 and the wheel 520.Operation of the balance mechanism 516 occurs in a manner substantiallysimilar to the example in FIGS. 1-9, with the cam member 550 convertinga variable force from the energy storage member 544 into a substantiallyconstant force for the mounting portion 506.

In the embodiment shown in FIGS. 18A-18C, the mounting portion 506 has atubular construction with a rectangular cross-section that enables themounting portion 506 to fit about the support column 504. The mountingportion 506 is movably coupled to the support column 504 with a guidesystem, including for example, rails within the support column andslides or rollers within the mounting portion. In some embodiments thetubular construction is symmetrical with respect to a longitudinal axisof the mounting portion, giving the mounting portion two pair ofsubstantially identical opposing faces. The tubular construction andopposing faces provide multiple options for mounting equipment, thusenabling the same lift mechanism 500 to be used in a number oforientations and positions (e.g., left side and/or right side, frontside and/or back side) without the need for a specially designedmounting portion for each possible position or orientation.

Referring to FIG. 18B, the lift mechanism 500 includes a brake mechanism552 that is attached to the mounting portion 506 and engages the supportcolumn 504 to hold the mounting portion 506 at a desired positionrelative to the support column. The brake mechanism 552 includes aplunger 554 configured to fit within a set of slots in the supportcolumn 504. Although not shown, the slots can extend along the length ofthe support column, at least along the range of travel 508 for themounting portion. A compression spring 556 urges the plunger 554 intothe slots, thus providing a normally braked configuration at one of manyvertical positions along the support column 504. According to someembodiments, the brake mechanism 552 can be temporarily disengaged bypulling the plunger 554 away from the support column, either directly orthough the use of a cable and lever system.

FIGS. 19A-19D are perspective views of a height adjustable desk 600incorporating the lift mechanism 500 shown in FIGS. 18A-18C inaccordance with an embodiment of the invention. As used herein, a“height adjustable desk” and a “height adjustable table” may also bereferred to as a display positioning apparatus in cases in which thedesk/table is configured to support an electronic display. For example,an electronic display may simply rest upon a work surface of a desk ortable, or the desk or table may include some other attachment mechanismfor supporting a display.

The desk 600, which may also be referred to as a table, includes a base602 supported by four feet 604. In some cases the feet 604 are heightadjustable (e.g., with a threaded post) to provide for fine leveling ofthe desk's work surface. Alternatively, the base 602 could not includefeet, or may optionally include casters. The base 602 is connected to afirst lift mechanism 610 and a second lift mechanism 612, positioned onopposite sides of the base. As discussed above, the lift mechanisms 610,612 each include a support column 614, a mounting portion 616, and abalance mechanism including multiple cams for balancing the forcesexerted by the energy storage member and the load being carried. In thisembodiment the balance mechanisms are provided in a covered housing 618.

The desk 600 further includes a work surface 620 having two side legs622. The legs 622 are configured to attach to the mounting portions 616.In this embodiment the legs 622 comprise three sides that attach tothree faces of the mounting portions 616. The three sides of the legs622 form a longitudinal recess in the leg with a rectangularcross-section that fits about the support columns 614 and allows thelegs to slide up and down about the support column. Of course, it shouldbe appreciated that this is just one example of a possibleconfiguration, and the legs 622 could be formed according to many otherconfigurations that allow the legs to attach to the mounting portions616. In addition, the legs 622 may be integrally formed with the worksurface 620 as shown in the figures (e.g., as a molded plasticcomponent), or may be separately formed and attached to the work surface620.

The height adjustable desk 600 also includes some optional features,including cable management holes 630 in the work surface 620 and abraking system. The braking system includes the brake mechanism of eachlift mechanism 610, 612 as described with respect to FIGS. 18A-18C,slots along the length of each support column, and a brake lever 640positioned on the underside of the work surface 620. The brake lever 640is coupled to the brake mechanisms with cables (not shown) routedthrough the legs 622 and attached to the plunger of each brakemechanism. Actuating the lever 640 pulls the plunger and disengages thebrakes from each support column 614. Relaxing the lever 620 allows theplunger of each brake mechanism to reengage the support column due tothe biasing force of the plunger spring. As shown in FIGS. 19A-19D, thesupport legs 622 include a brake housing 642 that accommodates andcovers the brake mechanism in each lift mechanism.

While the brake system is useful for arresting movement of the desk 600,it may not be included in all embodiments of the invention. For example,in some cases the lift force from each lift mechanism 610, 612, as wellas friction between the lift mechanisms' support columns and mountingportions will create sufficient force to offset the weight of the worksurface 620 and maintain the desk's position. In addition, when used,the brake lever can be located in any suitable location relative to thedesk 600, and may in some cases be proximate the base for footactuation.

Referring to FIGS. 19A and 19B, in use the desk work surface 620 can beraised and lowered through a generally vertical range of travel 650 thatprovide multiple height positions for the work surface 620. FIG. 19illustrates the adjustable desk 600 in a high position (e.g., forstanding), while FIG. 19B illustrates the desk 600 in a low position(e.g., for sitting). In one embodiment, the vertical range of travel 650extends between a sitting height and a standing height, thus allowing anoperator to use the desk 600 at a sitting position and a standingposition. For example, in certain embodiments the vertical range oftravel 650 is at least about 14 inches. In some embodiments the verticalrange of travel 650 is between about 14 inches and about 24 inches. Thelift mechanisms 610, 612 in the desk 600 may also provide multiplepositions at intermediate heights between the lowest and highest extentsof the range of travel 650, thus accommodating other working positionsand/or operators of different heights. In some cases a discrete numberof intermediate positions are provided. In some cases the liftmechanisms provide an infinite number of intermediate positions withinthe vertical range of travel 650.

FIGS. 20A-20D illustrate another example of a lift mechanism 700according to an embodiment of the invention. FIGS. 20E-20F illustrate asimilar example of the lift mechanism 700 with the balance mechanismhaving a slightly different configuration from the configuration shownin FIGS. 20A-20D. In general, the lift mechanism 700 has a telescopingconfiguration, which can be useful for limiting the height of the liftmechanism in its lowest position. In addition, the telescoping actioncan enable attachment of the lift mechanism 700 to the underside of asurface, away from the edges of the surface (e.g., at the center of thesurface).

FIG. 20A is a perspective view of the lift mechanism 700, while FIG. 20Bis a partial sectional view of the lift mechanism 700. The liftmechanism 700 includes a riser 702 that is formed from an inner tube 704and an outer tube 706. The inner tube 704 and the outer tube 706 arecoupled in a sliding engagement with a guide system including, forexample, rails and slides, glides, rollers, or any other suitablemechanism. As shown in FIGS. 20A-20B, the lift mechanism 700 is orientedsuch that the outer tube 706 can be attached to or rested upon a supportsurface and the inner tube 704 can be moved relative to the supportsurface and the outer tube 706. Accordingly, in some cases the outertube 706 can be considered a support column and the inner tube can beconsidered a mounting portion. In certain embodiments, though, the liftmechanism 700 can be positioned in an opposite orientation such that theinner tube rests upon or is attached to a support surface and the outertube 706 can be moved relative to the support surface and the inner tube704. In such a case the outer tube 706 can be considered the mountingportion while the inner tube 704 acts as the support column.

In the embodiment shown in FIGS. 20A-20B, the inner and the outer tubes704, 706 are slidingly engaged through a generally vertical range oftravel 708. As the inner tube 704 slides out from the outer tube 706,the overall length of the lift mechanism 700 increases, while as theinner tube slides back into the outer tube, the length of the liftmechanism decreases. Accordingly, the length of the lift mechanism 700adjusts as the inner tube 704 moves through the range of travel 708. Theadjusting length is useful for reducing the height of the lift mechanism700 when the lift mechanism is in a lower position. In addition, thelift mechanism does not require support column with a single, fixedlength that accommodates the entire range of travel 708 at the sametime.

Referring to FIGS. 20C-20F, the lift mechanism 700 includes an energystorage member 710 for providing lift assistance, which in this examplecomprises an extension spring. The energy storage member 710 ispositioned within the inner tube 704 and attached at the lower end 712of the inner tube, and thus moves up and down with the inner tube as theinner tube moves relative to the outer tube 706. An upper spring guide714 is provided at the opposite end of the storage member to guidemovement of the energy storage member as it extends and contracts. Thelift mechanism 700 also includes a balance mechanism 716 coupled betweenthe outer tube 706 and the energy storage member 710 for balancingforces between the energy storage member 710 and the outer tube 706. Asdiscussed above, in some cases the lift mechanism 700 provides adiscrete number of intermediate positions. In some cases the liftmechanism 700 provides an infinite number of intermediate positionswithin the vertical range of travel 708.

In this example, the balance mechanism 716 is similar to the balancemechanism 116 described above with respect to FIGS. 1-9. The balancemechanism 716 includes a wheel 718 that is rotationally coupled to a cammember 720 (shown in FIGS. 20E-20F) that includes two separate cams 721,723. A pulley system 722 includes dual cam pulleys 724, 726 that arecoupled to the cams via flexible elements (not shown) and an energystorage member pulley 728 coupled to the energy storage member 710 viaanother flexible element (not shown). Two direction-changing pulleysincluding a lower pulley 730 and an upper pulley 732 route anotherflexible element (not shown) between the outer tube 706 and the wheel718. FIGS. 20C-20D illustrate a first configuration in which the wheel718, cam member 720, pulley system 722, and upper pulley 732 are mountedrelative to the inner tube 704 with a bracket 740. FIGS. 20E-20Fillustrate a similar configuration with the order of the wheel and cammember, and the pulley system and upper pulley reversed. In operation,the cam member 720 converts a variable force from the energy storagemember 710 into a substantially constant force that lifts the inner tube704 relative to the outer tube 706.

Although not shown in FIGS. 20C-20F, multiple flexible elements couplethe parts of the balance mechanism 716 and the energy storage member710. According to one example, a first flexible element is attached tothe wheel 718 and routed over the upper pulley 732 down to the lowerpulley 730. The first flexible element then wraps around the lowerpulley 730 and is attached to an upper end 734 of the outer tube 706.Initially, when the lift mechanism 700 is in its highest position, thefirst flexible element is wrapped around the wheel 718. As the innertube 704 moves down, the first flexible element pulls and rotates thewheel 718, thus uncoiling the first flexible element and allowing thedown travel. In some cases the tension on the first flexible element isgenerally the same as the combined weight of the balance mechanism 716,the inner tube 704 and any equipment attached to the inner tube.

The wheel 718 is rotationally fixed with the cam member 720, and thuswhen the wheel 718 rotates, the cam member 720 also rotates. In thisexample a second flexible element (not shown) is routed from the each ofthe first and the second cams 721, 723 to the first and the second campulleys 724, 726 in a manner similar to the embodiment shown in FIG. 3B.Initially, the second flexible element is wrapped around the campulleys. As the wheel 718 and cam member 720 rotate, the first andsecond cams pull the second flexible element, which wraps around thecams 721, 723 and causes the cam pulleys to rotate. As discussed in theembodiments above, the use of the dual cams 721, 723 divides the tensionof the lift mechanism among the cams.

The energy storage member 710 is located inside the inner tube 704 andattached to the lower end 712 of the inner tube. A third flexibleelement (not shown) connects the energy storage member pulley 728 withthe upper end 744 of the energy storage member 710. As the cam pulleys724, 726 rotate, the third flexible element wraps around the energystorage member pulley 728, thus pulling the upper end of the energystorage member 710 and creating an increasing spring force. The tensionon the first flexible element (e.g., equal to the combined weight of themounted equipment, inner tube, and balance mechanism) applies asubstantially constant torque to the wheel 718. Each of the cams 721,723 converts half of the increasing spring force (applied to each camvia the second flexible element) to a substantially constant torqueequal to half of the torque carried by the wheel 718.

In some cases the energy storage member 710 is attached to the innertube 704 in an adjustable manner to enable adjustment of the tension ofthe energy storage member depending on the weight that needs to bebalanced. In this case, adjustment is achieved by controlling theposition of the lower end of the spring via the adjustment mechanism. Insome cases the adjustment mechanism can be based on a screw, warm gear,bevel gears, or other mechanism. Referring to FIG. 20E, in some casesthe lift mechanism 700 includes a brake mechanism 748, which in thisexample is similar to the brake mechanism example as described withrespect to FIGS. 18A-18C.

Turning to FIG. 20A, in some cases a work surface (or otherequipment/items) can be mounted at the top end 750 of the inner tube 704so that the balance mechanism 716 is attached to the work surface andpositioned directly below the work surface. Some advantages of thisconfiguration include freeing up space at the lower end 752 of the outertube 706 that acts as the base of the lift mechanism 700 and somewhatconcealing the balance mechanism with the work surface. While FIGS.20A-20F illustrate this configuration, it is also possible that the liftmechanism 700 could be turned upside down and the work surface could bemounted to the “lower” end 752 of the outer tube 706 while the “upper”end 750 of the inner tube acts as the base of the lift mechanism.

FIGS. 21A-21B and 21C-21D illustrate two examples of a height adjustabledesk incorporating the lift mechanism 700 shown in FIGS. 20A-20F inaccordance with embodiments of the invention. FIGS. 21A-21B are sideelevation views of a stationary height adjustable desk 800 in accordancewith an embodiment of the invention. The lift mechanism 700 is attachedto a base 802 at the lower end 752 of the outer tube 706. In thisembodiment the base 802 includes feet 803 for positioning the base on afloor or other surface. A work surface 804 is attached to the upper end750 of the inner tube 704 and the balance mechanism 716 and a housing806 surrounding the balance mechanism are located directly beneath thework surface 804. The height of the desk 800 is adjustable through arange of travel 808, including a high position (e.g., for standing)shown in FIG. 21A and a low position (e.g., for sitting) shown in FIG.21B. As discussed above, in some cases the lift mechanism 700 provides adiscrete number of intermediate positions. In some cases the liftmechanism 700 provides an infinite number of intermediate positionswithin the vertical range of travel 808.

As shown in FIGS. 21A-21B, use of the telescoping lift mechanism 700allows the work surface 804 to be positioned (e.g., centered) on top ofthe lift mechanism, which can advantageously reduce any cantileveringbetween the work surface and the lift mechanism. Reducing cantileveringhelps reduce friction in the guide system of the lift mechanism andlower the force needed by an operator to adjust the lift mechanism. Insome cases this can enable the use of a single lift mechanism whereasmultiple lift mechanisms may be necessary in other embodiments. Forexample, the embodiment described in FIGS. 19A-19D includes two liftmechanisms positioned near opposing edges of the work surface. In someembodiments, though, a single lift engine can be positioned near theedge of a work surface if sufficient structural features are present torespond to the cantilever load. For example, use of a longer truck andstronger support bracket under the work surface could allow a side mountconfiguration, although such features may increase costs.

FIGS. 21C-21D are perspective views of a movable height adjustable desk850 in accordance with an embodiment of the invention. The liftmechanism 700 is attached to a base 852 at the lower end 752 of theouter tube 706. In this embodiment the base 852 includes casters 853that enable movement of the desk across a floor or other surface. A worksurface 854 is attached to the upper end 750 of the inner tube 704 andthe balance mechanism and a housing surrounding the balance mechanismare located directly beneath the work surface 854. The height of thedesk 800 is adjustable through a range of travel 858, including a highposition (e.g., for standing) shown in FIG. 21C and a low position(e.g., for sitting) shown in FIG. 21D. As discussed above, in some casesthe lift mechanism 700 provides a discrete number of intermediatepositions. In some cases the lift mechanism 700 provides an infinitenumber of intermediate positions within the vertical range of travel858. FIG. 21D illustrates an optional keyboard tray 860 that may beattached to the work surface 854 in some embodiments.

Turning to FIGS. 22A-22C, another example of a lift mechanism 900 isillustrated according to an embodiment of the invention. FIG. 22A is across-sectional view of the lift mechanism 900, FIG. 22B is across-sectional view of a bottom portion of the lift mechanism 900, andFIG. 22C is a partial top view of the lift mechanism 900. The liftmechanism 500 includes a base 902 connected to a support column 904(sometimes referred to as a “riser”). A mounting portion 906 is movablycoupled to the support column 904 and configured to move up and down thesupport column 904 through a generally vertical range of travel 908. Inthis embodiment the mounting portion 906 comprises a three-sided bracketthat rides along one side of the support column 904, although otherconfigurations could also be used.

An energy storage member 944 is coupled to the mounting portion 906 forproviding lift assistance. In this embodiment, the energy storage member944 comprises a first extension spring 945 and a second extension spring947. The lift mechanism includes an upper spring guide and attachmentmember 943 that attaches the energy storage member to the supportcolumn. The member 943 also guides adjustment of the tension of theenergy storage member through an optional adjustment screw 946. Twolower spring guides 948 are provided at the opposite end of each of thefirst and second extension springs 945, 947 to guide movement of thesprings as they extend and contract. The lift mechanism 900 alsoincludes a balance mechanism coupled between the mounting portion 906and the energy storage member 944 for balancing forces between theenergy storage member 944 and the mounting portion 906.

In this example, the lift mechanism 900 includes a balance mechanism 916similar to the balance mechanism 116 described above with respect toFIGS. 1-9. Turning to FIG. 22B and 22C, the balance mechanism 916includes a wheel 920 that is rotationally coupled to a cam member 950that includes a first cam 924 and a second cam 926. A pulley system 930includes a first cam pulley 964 and a second cam pulley 968. The firstcam pulley 964 routes a first flexible element 931 that is coupled atone end to the first cam 924 and at the other end to the first extensionspring 945. The second cam pulley 968 routes a second flexible element932 that is coupled at one end to the second cam 926 and at the otherend to the second extension spring 947. A third flexible element 933 iscoupled between the wheel 920 and the mounting portion 906. Twodirection-changing pulleys including a lower pulley 934 and an upperpulley 938 (see FIG. 22A) route the third flexible element 933 betweenthe mounting portion 906 and the wheel 920.

Operation of the balance mechanism 916 occurs in a manner similar to theexample in FIGS. 1-9, with the cam member 950 converting a variableforce from the energy storage member 944 into a substantially constantforce for the mounting portion 906. However, in this embodiment thetotal lift force provided by the energy storage member 944 is providedby the two extension springs 945, 947 rather than a single extensionspring shown in FIGS. 1-9. The use of the two extension springs reducesthe necessary force provided by each spring (e.g., each spring canprovide half of the lift force), which also reduces the force carried byeach of the first and second flexible elements 931, 932. Also, since thenecessary force is reduced, the extension springs 945, 947 can be formedfrom a smaller diameter wire and have a slightly smaller radius thanwould be required with a single extension spring (e.g., 5-10 mm smallerradius). Accordingly, when the springs are arranged side-by-side, thelift mechanism 900 can have a width that is narrower than would benecessary with a single spring. Aligning the support column 904 in aboutthe same plane as the wheel 920 and cam member 950 thus provides anarrower configuration for the riser 900 that can provide more room foran operator in proximity to the riser 900.

FIGS. 23A-23B are views of a height adjustable desk 1000 incorporatingthe lift mechanism 900 shown in FIGS. 21A-21C in accordance with anembodiment of the invention. The lift mechanism 900 is attached to abase 1002 at a lower end of the support column 904. In this embodimentthe base 1002 includes feet 1003 for positioning the base on a floor orother surface. The mounting portion 906 of the lift mechanism isattached to a work surface 1004 along one side of the work surface andthe balance mechanism 916 and a housing 1006 surrounding the balancemechanism are located directly beneath the edge of the work surface1004. The height of the desk 1000 is adjustable through a range oftravel 1008, including a high position (e.g., for standing) shown in thefigures and a low position (e.g., for sitting). As discussed above, insome cases the lift mechanism 900 provides a discrete number ofintermediate positions. In some cases the lift mechanism 900 provides aninfinite number of intermediate positions within the vertical range oftravel 1008. An optional break mechanism 1020 can be included forstopping movement of the mounting portion 906 and the work surface 1004as described above.

As shown in FIGS. 23B, the lift mechanism 700 near a back edge 1030 ofthe desk 1000 in this embodiment. The coupling of the lift mechanismnear the back edge 1030 and the relatively narrow configuration of theriser 904 and balance mechanism housing 1006 combine to provide agreater amount of space underneath the work surface 1004 between theriser/balance mechanism and the front edge 1032 of the work surface1004. Thus an operator can sit facing the front edge 1032 and have agreater amount of leg room below the work surface 1004.

FIGS. 24A-24E illustrate a number of views of another height adjustabledesk 1100 according to an embodiment of the invention that is similar insome respects to the desk 1000 shown in FIGS. 23A-23B. FIGS. 24A-24B areperspective views of the height adjustable desk 1100 incorporating alift mechanism 1200 shown in more detail in FIGS. 24D-24E in accordancewith an embodiment of the invention. The lift mechanism 1200 is attachedto a base 1102 at a lower end of the support column 1204. In thisembodiment the base 1102 includes feet 1103 for positioning the base ona floor or other surface. The mounting portion 1206 is attached to awork surface 1104 along one side of the work surface and the balancemechanism 1216 and a housing 1208 surrounding the balance mechanism arelocated directly beneath the edge of the work surface 1104. The heightof the desk 1100 is adjustable through a range of travel 1108, includinga high position (e.g., for standing) shown in the figures and a lowposition (e.g., for sitting). As discussed above, in some cases the liftmechanism 1200 provides a discrete number of intermediate positions. Insome cases the lift mechanism 1200 provides an infinite number ofintermediate positions within the vertical range of travel 1108. Anoptional break system including a brake lever 1122 and a brake mechanism1124 can be included for stopping movement of the mounting portion 1206and the work surface 1104 as described above. Turning to FIG. 24C, acable 1126 can be routed through the lift mechanism between the lever1122 and the break mechanism 1124 for actuating the break mechanism.

FIG. 24D is a partial top view of the height adjustable desk 1100 thebalance mechanism housing 1208 removed, and FIG. 24E is a partial topview of the lift mechanism 1200. In this embodiment the lift mechanism1200 is similar to the lift mechanism shown in FIGS. 22A-22C andoperates in much the same way. For example, the lift mechanism 1200includes a support column 1204 and a mounting portion 1206, which inthis case comprises a flat planar member as opposed to the three-sidedmember shown in FIGS. 22A-22C. The energy storage member 1244 comprisesa first extension spring 1245 and a second extension spring 1247. Thelift mechanism 1200 also includes a balance mechanism coupled betweenthe mounting portion 1206 and the energy storage member 1244 forbalancing forces between the energy storage member 1244 and the mountingportion 1206. The balance mechanism 1216 similar to the balancemechanism 116 described above with respect to FIGS. 1-9 and includes awheel 1220 that is rotationally coupled to a cam member 1250 thatincludes a first cam 1224 and a second cam 1226. A pulley system 1230includes a first cam pulley that routes a first flexible element (notshown) that is coupled at one end to the first cam 1224 and at the otherend to the first extension spring 1245. A second cam pulley 1268 routesa second flexible element (not shown) that is coupled at one end to thesecond cam 1226 and at the other end to the second extension spring1247. A third flexible element (also not shown) is coupled between thewheel 1220 and the mounting portion 1206. Two direction-changing pulleysincluding a lower pulley and an upper pulley 1238 route the thirdflexible element between the mounting portion 1206 and the wheel 1220.Operation of the balance mechanism 1216 occurs in a manner similar tothe example in FIGS. 22A-22C, with the cam member 1250 converting avariable force from the two extension springs 1245, 1247 into asubstantially constant force for the mounting portion 1206.

As described herein, a number of positioning apparatuses and heightadjustable desks can incorporate a balance mechanism having two or morecams. Also, a number of examples of positioning apparatuses that mayinclude a balance mechanism having multiple cams is described inco-pending U.S. patent application Ser. No. ______, designated byattorney docket number 44374.95.2, titled Display Positioning Apparatusand Method, and filed concurrently herewith. The entire content of the44374.95.2 application is hereby incorporated by reference herein in itsentirety. While it is believed that a multi-cam balance mechanism canprovide advantages in certain circumstances, embodiments of theinvention are not limited to multi-cam balance mechanisms and mayalternatively include a single cam balance mechanism. For example, thepositioning apparatuses 300, 400, and 450 shown in FIGS. 12A-13B and16A-17 could incorporate a lift mechanism including a single cam balancemechanism. In addition, embodiments of the invention include the liftmechanisms and height adjustable desks shown in FIGS. 18A-24Bincorporating a single cam balance mechanism as an alternative to amulti-cam (e.g., dual cam) balance mechanism. A single-cam balancemechanism can be any suitable mechanism known in the art. In someembodiments, a single-cam balance mechanism includes a mechanism such asone of those taught in presently co-owned US Patent ApplicationPublication US 2006/0185563 A1, which application was filed Sep. 28,2005, the entire contents of which is incorporated by reference herein.

In addition, several optional accessories and/or features can beincorporated into any of the lift mechanisms, positioning apparatuses,and/or height adjustable desks described herein. Several examples offeatures and accessories will now be described.

According to some embodiments, a lift mechanism for a positioningapparatus includes a base that is configured to sit directly on a worksurface, such as a desk or table. In certain cases the base isconfigured to attach (e.g., removably or fixedly) to the work surface.In some cases a positioning apparatus includes one or more mountingbrackets (e.g., a cross bar, etc.) configured to attach various piecesof equipment to the lift mechanism. One embodiment includes a smallindependent work surface attached to the moving portion of a liftmechanism separate from a keyboard tray. One embodiment includes a mountfor an electronic display and a keyboard tray configured to support akeyboard. In some cases the lift mechanism is configured to move thedisplay mount and the keyboard tray in tandem. The display mount may befixed relative to the keyboard tray or there may be an independent liftmechanism for changing the vertical distance between the display mountand the keyboard tray. In some embodiments the keyboard tray is fixed,while in certain cases it may be configured to fold back in order toprovide more space for an operator when the keyboard is not in use. Insome embodiments the keyboard tray is configured as a larger worksurface which can also be used for writing, reading, etc. In addition,in some embodiments the keyboard tray may be fixed in a horizontalrelationship with respect to a display mount. Alternatively, thekeyboard tray may be attached to a horizontally moving bracket to varythe horizontal distance between the display mount and the operator. Insome embodiments the lift mechanism is configured to counter balance thecombined weight of any moving portions of the lift mechanism along withany attached equipment. In some embodiments the counter balancing forceis adjustable by the operator.

According to some embodiments, a height adjustable desk is configured toposition the desk surface in both a sitting position and a standingposition to provide a sit-to-stand desk. In some embodiments, the desksurface can be adjusted by about 14-20 inches in order to providesit-to-stand capability. According to some embodiments, the weight ofthe desk surface and any equipment located on the desk surface iscounterbalanced by using one or more lift mechanisms, thereby providinglift assistance to an operator and lowering the forces needed to adjustthe height of the desk surface. In some cases one or more of the liftmechanisms are weight adjustable to increase or decrease the counterbalance force in order to more closely match the weight of the desk andany equipment on the desk. According to some embodiments, one or morelift mechanisms can be attached to the bottom of the desk surface at oneor more locations, including side edges, corners, a back edge, or awayfrom edges toward the center of the desk surface. Any suitable equipmentcan be supported by the desk surface, including but not limited to, acomputing device, a notebook, a desk stand or arm to hold a number ofmonitors, a telephone, a document holder, and any other items known inthe art.

In certain embodiments, a height adjustable desk can include one of manytypes of lift mechanisms, including those with a telescoping,non-telescoping, and/or pseudo-telescoping configuration. In some casesa balance mechanism can be located within a riser (e.g., supportcolumn), adjacent to the riser, under a work surface, or inside the basewith a guide system located on the riser. In some cases a balancemechanism includes a rotary cam member coupled with an energy storagemember that includes one or more springs. Many types of springs can beused, including extension springs, compression springs, torsion springs,and/or spiral springs. The guide system that couples a mounting portionto a support column can include one or more slides in each riser or mayinclude rollers. The guide system can be oriented in various directions,including forward facing, sideways, or at any angle in between. In somecases a relatively strong attachment structure (e.g., a bracket)attaches a riser and guide system to a desk surface, thus reducing oreliminating the need for synchronizing multiple risers and guidesystems.

According to some embodiments, a height adjustable desk may include adisplay mount attachment and/or a keyboard tray attachment. In somecases, the display mount attachment can be a height adjustable or fixedheight free standing display stand that sits upon the desk surface. Insome cases the display mount attachment includes a clamp on arm thatcould be height adjustable or fixed height. In some cases the displaymount attachment is attached to the work surface with one or morefasteners (e.g., bolts, screws, etc.) In addition, any display mountattachment can be configured for one, two, three, or more electronicdisplays, or may be configured for one or more displays and/or anotebook computer. A keyboard tray attachment can in some cases beclamped on to the work surface, or may be fixedly attached with screws,bolts, etc. In some embodiments, such as those shown above, the worksurface may include openings that enable cable management. Someembodiments also include a brake system incorporating a brake mechanismand a brake lever coupled by a cable. The brake lever can be located inany suitable location and may be hand or foot actuated. In certain casesthe base of a height adjustable desk includes height adjustable feet orcasters. In certain embodiments, the desk may also include one or moreof a document holder, a telephone holder, and a computer case holder.

Embodiments of the invention also include methods of positioningequipment, such as a display, keyboard, and/or work surface. Accordingto one embodiment, a method of positioning a display includes lifting adisplay within a vertical range of travel and assisting the lifting ofthe display with a variable force exerted by an energy storage member.In some cases the method also includes converting the variable forceexerted by the energy storage member into a substantially constant forceapplied to the display with a balance mechanism. The balance mechanismcan comprise any of the balance mechanisms described herein. In oneembodiment, the balance mechanism comprises a first cam, a second camrotationally coupled to the first cam, and a wheel rotationally coupledto the first cam and the second cam. The first cam and the second camare configured to convert the variable force exerted by the energystorage member into a substantially constant force applied to thedisplay. Such a method can be carried out by articulating any of thelift mechanisms, display positioning apparatuses, and height adjustabledesks described herein.

In some embodiments, a method also includes lowering the display withinthe vertical range of travel and resisting the lowering of the displaywith an additional variable force exerted by the energy storage member.In this case, the first cam and the second cam are configured to convertthe additional variable force exerted by the energy storage member intoa substantially constant force applied to the display. For example, asthe energy storage member 144 of FIG. 109 contracts, it provides avariable force that resists movement of the mounting portion of the liftmechanism. According to some embodiments, converting the variable forceto a substantially constant forces allows the position of the displaywithin the vertical range of travel to be maintained without a brakemechanism.

Moving a display can occur in any suitable manner depending upon theconfiguration of the lift mechanism (e.g., corresponding to thosemechanisms described above.). In some embodiments, lifting the displaycomprises moving a mounting portion relative to a support column. Incertain cases, moving the mounting portion relative to the supportcolumn includes moving an inner tube within and relative to an outertube, such as in the example of a telescoping lift mechanism shown inFIGS. 20A-21D. In some cases, the display may be positioned on orattached to a movable work surface (e.g., as part of a height adjustabledesk) and moving the display including moving the movable work surfacerelative to the support column.

Thus, embodiments of the invention are disclosed. Although the presentinvention has been described in considerable detail with reference tocertain disclosed embodiments, the disclosed embodiments are presentedfor purposes of illustration and not limitation and other embodiments ofthe invention are possible. One skilled in the art will appreciate thatvarious changes, adaptations, and modifications may be made withoutdeparting from the spirit of the invention and the scope of the appendedclaims.

1. A lift mechanism, comprising: a base; a support column coupled to thebase; a mounting portion movably coupled to the support column; anenergy storage member coupled to the support column; and a balancemechanism coupled between the energy storage member and the mountingportion, the balance mechanism comprising a first cam, a second camrotationally coupled to the first cam, and a wheel rotationally coupledto the first cam and the second cam, wherein the first cam and thesecond cam are configured to convert a variable force exerted by theenergy storage member into a substantially constant force applied to themounting portion.
 2. The lift mechanism of claim 1, wherein the firstcam, the second cam and the wheel are coaxially mounted to the base. 3.The lift mechanism of claim 2, wherein the first cam has a radius thatvaries with rotation and the second cam has a radius that varies withrotation.
 4. The lift mechanism of claim 3, further comprising a cammember comprising the first cam and the second cam.
 5. The liftmechanism of claim 4, wherein the cam member comprises an axis ofrotation and the first cam and the second cam are symmetrically formedabout a plane perpendicular to the axis of rotation.
 6. The liftmechanism of claim 3, wherein the first cam and the second cam eachcomprise an axis of rotation and a cam surface that winds about the axisof rotation, and wherein the radius of each of the first cam and thesecond cam decreases as the cam surface winds between a perimeter of thecam and the rotational axis of the cam, wherein the decreasing radius isconfigured to match a variable force profile of the energy storagemember.
 7. The lift mechanism of claim 1, wherein the balance mechanismfurther comprises a pulley system, the pulley system comprising a firstcam pulley and a second cam pulley that route one or more flexibleelements between the first and the second cams and the energy storagemember.
 8. The lift mechanism of claim 7, wherein the pulley systemfurther comprises an energy storage member pulley, wherein the first campulley, the second cam pulley, and the energy storage member pulley arerotationally coupled, further comprising at least one flexible elementcoupling the first cam pulley to the first cam and the second cam pulleyto the second cam, and further comprising at least one additionalflexible element coupling the energy storage member pulley with theenergy storage member.
 9. The lift mechanism of claim 8, wherein thefirst cam pulley, the second cam pulley and the energy storage memberpulley are integrally formed.
 10. The lift mechanism of claim 8, whereinthe at least one flexible element coupling the first cam pulley to thefirst cam and the second cam pulley to the second cam comprises a firstflexible element coupling the first cam pulley to the first cam and asecond flexible element coupling the second cam pulley to the secondcam.
 11. The lift mechanism of claim 7, wherein the one or more flexibleelements comprises a first flexible element coupled between the firstcam and the energy storage member and a second flexible element coupledbetween the second cam and the energy storage member.
 12. The liftmechanism of claim 11, wherein the energy storage member comprises afirst extension spring and a second extension spring, and wherein thefirst flexible element couples to the first extension spring to thefirst cam and the second flexible element couples the second extensionspring to the second cam.
 13. The lift mechanism of claim 1, wherein thefirst cam receives about half of the variable force exerted by theenergy storage member and the second cam receives about half of thevariable force exerted by the energy storage member.
 14. The liftmechanism of claim 1, wherein the mounting portion comprises a tubularconfiguration that fits about the support column.
 15. The lift mechanismof claim 1, wherein the support column comprises a first tube and themounting portion comprises a second tube in sliding engagement with thefirst tube.
 16. The lift mechanism of claim 15, wherein the first tubeis an outer tube and the second tube is an inner tube received withinthe outer tube.
 17. The lift mechanism of claim 1, further comprising anadjustment mechanism configured to adjust a tension of the energystorage member.
 18. The lift mechanism of claim 1, further comprising abrake mechanism coupled to the support column and configured to hold aposition of the mounting portion relative to the support column.
 19. Adisplay positioning apparatus comprising: a base; a support columncoupled to the base; a mounting portion movably coupled to the supportcolumn, the mounting portion comprising a display mount for attaching anelectronic display; an energy storage member coupled to the supportcolumn; and a balance mechanism coupled between the energy storagemember and the mounting portion, the balance mechanism comprising afirst cam, a second cam rotationally coupled to the first cam, and awheel rotationally coupled to the first cam and the second cam, whereinthe first cam, the second cam and the wheel are coaxially mounted to thebase and the first cam and the second cam are configured to convert avariable force exerted by the energy storage member into a substantiallyconstant force applied to the mounting portion.
 20. The displaypositioning apparatus of claim 19, wherein the first cam has a radiusthat varies with rotation and the second cam has a radius that varieswith rotation.
 21. The display positioning apparatus of claim 20,further comprising a cam member comprising the first cam and the secondcam.
 22. The display positioning apparatus of claim 21, wherein the cammember comprises an axis of rotation and the first cam and the secondcam are symmetrically formed about a plane perpendicular to the axis ofrotation.
 23. The display positioning apparatus of claim 20, wherein thefirst cam and the second cam each comprise an axis of rotation and a camsurface that winds about the axis of rotation, and wherein the radius ofeach of the first cam and the second cam decreases as the cam surfacewinds between a perimeter of the cam and the rotational axis of the cam,wherein the decreasing radius is configured to match a variable forceprofile of the energy storage member.
 24. The display positioningapparatus of claim 19, wherein the balance mechanism further comprises apulley system, the pulley system comprising a first cam pulley, a secondcam pulley, and an energy storage member pulley, wherein the first campulley, the second cam pulley, and the energy storage member pulley areintegrally formed about a single axis of rotation.
 25. The displaypositioning apparatus of claim 19, wherein the mounting portion furthercomprises a keyboard tray configured to support a keyboard.
 26. Thedisplay positioning apparatus of claim 25, wherein the mounting portioncomprises a second lift mechanism configured to move the display mountvertically relative to the keyboard tray.
 27. The display positioningapparatus of claim 19, wherein the mounting portion comprises at leastone of a mouse tray, a document holder, a movable work surface, and atelephone holder.
 28. The display positioning apparatus of claim 19,wherein the mounting portion comprises a plurality of display mounts forattaching a corresponding plurality of electronic displays to themounting portion.
 29. The display positioning apparatus of claim 28,wherein at least one of the plurality of display mounts furthercomprises a tilt mechanism and/or a rotation mechanism.
 30. The displaypositioning apparatus of claim 19, wherein the mounting portioncomprises a notebook tray and/or a notebook docking station.
 31. Aheight adjustable desk, comprising: a base; a work surface; and at leastone lift mechanism coupled between the base and the work surface, the atleast one lift mechanism comprising a support column coupled to thebase, a mounting portion movably coupled to the support column andfixedly coupled to the work surface, an energy storage member coupled tothe support column, and a balance mechanism coupled between the energystorage member and the mounting portion, the balance mechanismcomprising a first cam, a second cam rotationally coupled to the firstcam, and a wheel rotationally coupled to the first cam and the secondcam, wherein the first cam and the second cam are configured to converta variable force exerted by the energy storage member into asubstantially constant force applied to the mounting portion.
 32. Theheight adjustable desk of claim 31, wherein the first cam has a radiusthat varies with rotation and the second cam has a radius that varieswith rotation.
 33. The height adjustable desk of claim 32, furthercomprising a cam member comprising the first cam and the second cam. 34.The height adjustable desk of claim 33, wherein the cam member comprisesan axis of rotation and the first cam and the second cam aresymmetrically formed about a plane perpendicular to the axis ofrotation.
 35. The height adjustable desk of claim 32, wherein the firstcam and the second cam each comprise an axis of rotation and a camsurface that winds about the axis of rotation, and wherein the radius ofeach of the first cam and the second cam decreases as the cam surfacewinds between a perimeter of the cam and the rotational axis of the cam,wherein the decreasing radius is configured to match a variable forceprofile of the energy storage member.
 36. The height adjustable desk ofclaim 30, wherein the balance mechanism further comprises a pulleysystem, the pulley system comprising a first cam pulley, a second campulley, and an energy storage member pulley, wherein the first campulley, the second cam pulley, and the energy storage member pulley areintegrally formed about a single axis of rotation.
 37. The heightadjustable desk of claim 31, wherein the mounting portion is fixedlycoupled to the work surface proximate an edge of the work surface. 38.The height adjustable desk of claim 31, wherein the mounting portion isfixedly coupled to the work surface proximate a center of the worksurface.
 39. The height adjustable desk of claim 38, wherein the supportcolumn comprises a first tube and the mounting portion comprises asecond tube in sliding engagement with the first tube.
 40. The heightadjustable desk of claim 31, wherein the at least one lift mechanismcomprises a first lift mechanism and a second lift mechanism.
 41. Amethod of positioning a display, comprising: lifting the display withina vertical range of travel; assisting the lifting of the display with avariable force exerted by an energy storage member; and converting thevariable force exerted by the energy storage member into a substantiallyconstant force applied to the display with a balance mechanismcomprising a first cam, a second cam rotationally coupled to the firstcam, and a wheel rotationally coupled to the first cam and the secondcam, wherein the first cam and the second cam are configured to convertthe variable force exerted by the energy storage member into thesubstantially constant force applied to the display.
 42. The method ofclaim 41, further comprising lowering the display within the verticalrange of travel and resisting the lowering of the display with anadditional variable force exerted by the energy storage member, thefirst cam and the second cam configured to convert the additionalvariable force exerted by the energy storage member into a substantiallyconstant force applied to the display.
 43. The method of claim 41,further comprising maintaining a position of the display within thevertical range of travel with the balance mechanism and the energystorage member.
 44. The method of claim 41, wherein lifting the displaycomprises moving a mounting portion relative to a support column. 45.The method of claim 44, wherein moving the mounting portion relative tothe support column comprises moving an inner tube within and relative toan outer tube.
 46. The method of claim 41, wherein lifting the displaycomprises moving a movable work surface relative to a support column.